Genetic diversity and population structure of pummelo (Citrus maxima) germplasm in China

Pummelo (Citrus maxima) is one of the basic species of Citrus. It has been cultivated for about 4000 years in China, and therefore, there are abundant germplasm during the long time of culture. However, there is still a lack of a detailed study of the genetic characteristics of pummelo population. In this study, genetic diversity and population structure among 274 pummelo accessions collected in China were analyzed using 31 nuclear simple sequence repeat (nSSR) markers. The observed heterozygosity was calculated as 0.325 and genetic differentiation Fst as 0.077. Genetic structure analysis divided the whole germplasm into three subpopulations, Pop-a, Pop-b, and Pop-c. Pop-a was composed of accessions mostly from Southeast China, Pop-b was composed of accessions from the central region of South China, and Pop-c was composed of accessions from Southwest China. Meanwhile, the analysis of principal coordinate analysis and neighbor-join tree supported the viewpoint of three subpopulations, and then the possible dispersal routes of pummelos in China were proposed. This study provides an insight into the genetic diversity, facilitates future genome-wide association studies, and promotes the breeding program of pummelo as well.